1. Field of the Invention
The invention relates to a tray for retaining disks, such as glass disks used in storage devices, during processing of the disks.
2. Background Information
Circular-shaped magnetic disks are typically used in hard disk drives of computers, for example, for use in data storage applications. Such magnetic disks may be formed from aluminum, or from glass, for example, and will typically have a magnetic surface coating located thereon. A head of the disk drive interacts with the magnetic surface coating to read and write information to the disk. Such magnetic disks have achieved storage capacities of several gigabytes or more, using current technology.
Typically, the head of the disk drive that reads and writes information to the disk is arranged to float a small distance above a surface of the disk. By bringing the head closer to the surface of the disk, higher density recording becomes possible.
As mentioned, often the magnetic disks are formed from aluminum. However, aluminum is relatively soft, so when it is handled, it is possible to ding the disk and form an area where data cannot be retrieved from. Further, the aluminum is typically coated with a nickel plating to give the disk more stiffness and a harder surface. However, the nickel plating has a tendency to become magnetic, causing errors in reading and writing to the disk. Additionally, aluminum disks are limited in how smooth their surfaces can be made. The smoother a magnetic disk can be made, the closer the head can be brought to the surface of the disk during the read/write operations.
To overcome the problems associated with aluminum disks, attention has been directed to the utilization of glass disks, formed from sodium lithium glass, for example. However, the disk is typically spun at speeds of 7,000 to 10,000 revolutions per minute and higher. Since the disk is typically accelerated rapidly to, and decelerated rapidly from these speeds, the conventional glass disk is subject to breakage due to the stresses generated during spin-up and slow-down of the disk.
Further, glass disks are subject to breakage simply due to the fragile and brittle nature of glass. That is, if the glass disk is subjected to a shock, it may shatter and break.
Thus, there is a need for a glass disk that has increased strength and shock resistance, to reduce breakage to the disk.
Further, glass disks are prone to developing surface cracks. These surface cracks can spread, eventually weakening the disk sufficiently to cause it to fail. Thus, there is a need for a glass disk that stops or prevents surface crack propagation.
It is also known to strengthen glass (such as so-called bullet proof glass), using for example, chemical strengthening processes. However, the strengthening of glass disks used in data storage applications is problematic, in that handling or securing of the disks during treatment can cause minute defects on the surface of the glass disk, leading to the occurrence of read/write errors when using such disk.
Therefore, there is a need for a way of strengthening glass disks that will not damage or harm the glass disks during the process.
Furthermore, there is a demand for an inexpensive glass disk that can be manufactured in large quantities. Thus, there is a need for a way of simultaneously strengthening a large number of glass disks. Moreover, there is a need for a glass disk strengthening process that is adapted to be performed using automation.
It is, therefore, a principle object of this invention to provide a tray for retaining disks.
It is another object of the invention to provide a tray for retaining disks that solves the above mentioned problems.
These and other objects of the present invention are accomplished by the tray for retaining disks disclosed herein.
In an exemplary aspect of the invention, a tray is used to secure glass disks in a chemical strengthening process. The glass disks are chemically strengthened to make the disks stronger and stiffer, which minimizes the amount of flutter as the disks are spun in use.
In order to prevent a defect at a point of contact between the tray and the disk, in a further exemplary aspect of the invention, the disk and tray have similar thermal characteristics. That is, if the disk and tray had significantly different thermal characteristics, upon removing the tray and the disks from the bath, the disks would cool much more rapidly than the tray. Thus, heat from the tray could concentrate at the points of contact between the tray and the disks, causing defects at the points of contact. Providing the tray with similar thermal characteristics to the disk advantageously prevents defects at the points of contact, for example, on the periphery of the disk.
In another exemplary aspect of the invention, the tray is entirely formed of titanium, since titanium has thermal characteristics (i.e., coefficient of thermal expansion and thermal conductivity) very similar to the glass of the disks. Although the thermal characteristics are not identical, titanium can advantageously be tailored to have a desired configuration, will withstand the prolonged heat of the salt bath, and is more similar in its thermal characteristics to the glass disk than other potential materials for the trays, such as stainless steel. By matching the thermal characteristics of the glass, the glass disk and the tray will expand and contract in a similar manner, and will heat up and cool down at a similar rate.
In a further aspect of the invention, the tray includes one or more longitudinally extending solid rods disposed at a bottom, for example, of the tray. The solid rods will advantageously provide the tray with the desired strength and rigidity.
In another exemplary aspect of the invention, the tray includes at least one support plate that connects the rods together. For example, the tray may include four equally spaced, parallel support plates. By providing four support plates, the support plates can be located without interfering with the placement of the glass disks from the process cassettes (i.e., cassettes used to transport the disks during other procedures). That is, with a tray that is adapted to accommodate the glass disks from three process cassettes, the intermediate support plates can be located at junctions defined by adjacent process cassettes.
In another exemplary aspect of the invention, each support plate has the rods attached to a bottom thereof, for example. Further, each support plate has a notch formed therein, and at a location above the rods. The notches allow the trays to be slid over support members attached to a panel, to facilitate the automation of the chemical strengthening process.
In yet another aspect of the invention, the tray includes one or more disk-supporting members attached to the support plates, for example. The disk-supporting members are disposed to contact the outer peripheral edge of the respective glass disks in an engaging manner, to hold the disks upright (on their edges) during the chemical strengthening procedure.
Further, in order to ensure that the glass disks cool at about the same rate as the points of contacts of the tray, in a further exemplary aspect of the invention, the disk supporting members are wires tailored to have a zigzag (i.e., saw tooth) shape. Thus, each wire has a plurality of teeth, and a plurality of valleys disposed between adjacent teeth. In use, an outer peripheral edge of the glass disk is disposed in a respective valley, to help secure the glass disk to the tray.
In an exemplary aspect of the invention, the wires are relatively thick, and have a rectangular cross-sectional profile, although other cross-sectional profiles are also within the scope of the invention. For example, the wires may have a cross-sectional dimension of about 0.5 to 1.5 millimeters by about 0.5 to 1.5 millimeters. By being relatively thick, the wires are provided with sufficient rigidity and strength to support the various glass disks.
Moreover, in another aspect of the invention, the wires are open at all sides. Thus, the wires will tend to cool at about the same rate as the glass disks, thereby preventing the occurrence of hot spots. As a result, glass disks can be formed having superior characteristics.
In an exemplary aspect of the invention, there are three spaced apart zigzag wires, each being in contact with an outer periphery of the glass disk. The use of three wires helps to ensure that the glass disk will be retained in an upright position without tipping over. One of the wires is arranged between the support rods, so as to contact the disk at a lowermost peripheral portion thereof, at 0 degrees. The other two wires are disposed on opposite sides of the lowermost wire, to contact the outermost peripheral edge of the glass disk at an intermediate position, such as a position greater than 0 degrees and less than 90 degrees relative to the lowermost wire, for example. In an exemplary aspect of the present invention, the other two wires are arranged to contact the outer periphery of the glass disk offset to the lowermost wire by between about 70 and 80 degrees. Thus, and moving clockwise, if the lowermost wire is at 0 degrees on the circumference of the glass disk, the next wire will be disposed between about 70 and 80 degrees, and the next wire will be disposed between about 280 and 290 degrees. This configuration ensures that the wires contact the edges of the glass disk below a center line of the disk (i.e., a line passing through the 3:00 and 9:00, or 90 degree and 270 degree positions of the disk). That is, if the wires contacted the glass disk at or above the center line, the forces generated from the expanding and contracting components could forcibly push the disk down into the lowermost wire, causing possible deformities in, or breakage of the disk. By arranging the wires in the described manner, the forces will tend to push the disk upward, thus preventing the accumulation of undesirable stresses.
Further, if a plurality of wires are provided, the wires may be arranged so that the teeth and valleys of the respective wires are in registration with each other. This will allow the glass disks to be held in an essentially upright position, when placed in the correct valleys.
Further, in another exemplary aspect of the invention, each wire is zigzagged so that the teeth lie within a plane that projects through a center of the disks. That is, each tooth of the wire is arranged to point toward a center of the respective disks. This configuration ensures that the outer peripheral edge of the disk will not become hung up or caught in the teeth.
In an exemplary aspect of the invention, the radius of the valleys in the saw tooth pattern of the wire is selected so that the wire does not xe2x80x9cpinchxe2x80x9d the edges of the disk as the tray and the disk are heated and cooled. This ensures that the glass disk will not become stuck within the valleys of the wires during the expansion and contraction of the various components.
Moreover, in another aspect of the invention, the teeth are arranged to provide the valleys with a V-shaped configuration. This arrangement helps guide or channel the glass disks into position toward a base of the valleys. Moreover, since the sides of the teeth project outward away from the valley, this configuration ensures that the sides of the teeth do not come into contact with the surfaces of the glass disks.
In another aspect of the invention, the teeth of the wires are arranged with a spacing similar to the process cassettes, for example, a quarter inch spacing. Thus, the tray can easily accommodate three, for example, process cassettes of glass disks arranged end to end. Therefore, in an automated process, a mandrel can be used to move the process cassettes into and out of engagement with the tray, with a minimum of human intervention.
In yet a further aspect of the invention, the wires are attached to the support plates using rails that extend parallel to the wires. The rails provide added support to the wires, without significantly increasing the heat retention of the wires. Further, the wires may be connected to the rails using spaced connecting wires, each of which extends from the respective wire to the respective rail. The connecting wires help to keep the wires separated from the rails, maintaining the open framework of the wires.
In another aspect of the invention, the rails may be tipped up so that they are perpendicular to the edge of the disk. This helps ensure that the teeth of the wires point directly toward the center of the disk, ensuring that the disk does not get jammed or caught in the wires. That is, as the components expand and contract, the disk can move up and down.
In an exemplary aspect of the invention, the various parts of the tray are cut to shape using a laser. Thus, for example, a rail and a respective wire can be cut from a single plate of material. This results in a structure that is relatively strong, and eliminates any need to fasten the wires to the rails using other means, such as welding. Moreover, cutting the undulating shape of the wires using a laser prevents the occurrence of bending stresses that may accumulate at the bends of the wires, which may otherwise cause the wires to break.
In an exemplary aspect of the invention, the panel is adapted to accommodate an array of 8 columns by 10 rows of trays. Moreover, a like number of trays can be accommodated on an opposite side of the panel. Thus, in a relatively small volume of space, for example, 40 cubic feet, and with a tray adapted to accommodate 75 glass disks, a fully loaded panel can treat up to 12,000 glass disks simultaneously.
Due to the configuration of the trays, the locating of the disks into the tray, and the sliding of the trays onto the panel, the chemical strengthening process, the placement of the glass disks into the tray, and the removing of the glass disks from the tray can be performed automatically.